1. Field of the Invention
The present disclosure relates generally to semiconductor lasers, laser controllers, laser projection systems, and other optical systems incorporating semiconductor lasers. More particularly, by way of illustration and not limitation, embodiments of the present disclosure relate generally to optical alignment in packages that include, inter alia, a semiconductor laser and a wavelength conversion device, such as second or third harmonic generation crystal or another type of wavelength conversion device.
2. Technical Background
Short wavelength light sources can be formed by combining a single-wavelength semiconductor laser, such as an infrared or near-infrared distributed feedback (DFB) laser, distributed Bragg reflector (DBR) laser, or Fabry-Perot laser, with a light wavelength conversion device, such as a second harmonic generation (SHG) crystal. The SHG crystal is used to generate higher harmonic waves of the fundamental laser signal. To do so, the lasing wavelength is preferably tuned to the spectral center of the wavelength converting SHG crystal and the output of the laser is preferably aligned with the waveguide portion at the input facet of the wavelength converting crystal.
Waveguide mode diameters of typical wavelength conversion devices, such as MgO-doped periodically poled lithium niobate (PPLN) crystals, can be in the range of a few microns. As a result, it can be very challenging to align the beam from the laser diode with the waveguide of the SHG crystal properly. Accordingly, a variety of adaptive alignment mechanisms have been developed to steer the beam spot of the long wavelength source into proper alignment with the input facet of the waveguide portion of the wavelength conversion device.